Polyurethane foams are widely used in a variety of applications. For some applications, the polyurethane foam is sold in the form of a spray foam which can be used for various do-it-yourself applications, such as for sealing and insulation.
However, various environmental, health, and safety organizations require special labeling of polyurethane foams that include an isocyanate monomer level of greater than 1% by weight for at least one of its isocyanate components. In order to avoid this labeling requirement, some methods of forming the polyurethane prepolymer include a step of removing excess isocyanate monomer after reacting diisocyanate with a polyol. However, this additional processing can be time-consuming and costly. Accordingly, there is a need for polyurethane foam prepolymers that include low isocyanate monomer content without a separation step.